Fans of Halo know Master Chief can't receive all the credit for saving the world from extraterrestrial forces. After all, Master Chief may have handled the brawn of fighting the Covenant, the Forerunners, and the Flood. However, it's his AI Cortana that handled the brains of the entire operation. Despite her presence as a guiding voice, Cortana served as a smart artificial intelligence originally designed to assist the ship Pillar of Autumn.
Cortana was designed to be capable of managing various starships as well as infiltrating computer systems. Moreover, her advanced technological skillset became Master Chief's go-to when assessing combat data and accessing his various weapons. However, Cortana appears to have more secrets than just being Master Chief's "partner-in-crime."
10 Cortana Is A Smart AI
First things first, it's important to distinguish Cortana's status as an AI in the Halo universe. Unlike other AIs, people consider Cortana as a Smart AI. In the real world, such a definition might be difficult to comprehend. After all, AI should be inherently smart, right? However, by definition, Smart AIs have the ability to bypass their dynamic memory-processor matrix. In layman's terms, Smart AI learn not just through the information put in them. Instead, Smart AI eventually get the capabilities to analyze data from their surroundings. Oppositely, "dumb" AI simply processes vast amounts of information given to them.
However, the creation of "dumb" AI and Smart AI remains the same. Instead of "programming" AI like in the real world, Halo scientists "create" AI by replicating the neural pathways of the human brain. In Halo, scientists call this process Cognitive Impression Modeling. Unfortunately, this process destroys the brain tissue of the brain being replicated.
9 Cortana May Have Been Created Illegally
In Halo, medical practitioners use flash cloning to rapidly accelerate cloned body parts and organs so they can become of the same age as their owners. Theoretically, doctors can then transplant these organs with virtually zero chances of rejection. Interestingly, aside from this element, flash cloning may become a method to circumvent one of the "cons" of creating smart AI - the destruction of the donor organ.
Remember, AIs become "smart" by copying the neural patterns of a donor organ. However, as this process destroys the donor's brain, scientists often use diseased brains in the creation of Smart AI. However, Dr. Catherine Halsey created Cortana, not with her own brain patterns. Instead, she flash cloned her brain, which she then used to create Cortana. However, since Dr. Halsey didn't get authorization to flash clone her brain, this process is therefore technically considered illegal by UNSC standards.
8 Cortana Was Built To End The War
Interestingly, Cortana didn't serve as an "ordinary" ship AI. Rather, Dr. Halsey originally built AI specifically for Operation: RED FLAG. Supposedly, RED FLAG had the means of ending the Human-Covenant War by sacrificing a planet and forcing a truce with the Covenant. Moreover, they would achieve this by having a "specialist" infiltrate a Class-Five Covenant vessel and use the Covenant Prophet inside as a negotiating tool.
In turn, Dr. Halsey created Cortana to have the role of that specialist. This purpose may explain why Cortana has a vast array of abilities that far exceed ordinary ship AI or as an armor-installed assistant. Unfortunately, Cortana will never get to fulfill that role given the Fall of Reach.
7 Cortana Had Complicated Relationships With Humans
Unfortunately, Cortana's Rampancy made her see humans in a different light. In fact, it's seeing humans and their constant "war-like" nature that motivated Cortana to assume control over the Mantle of Responsibility.
In the case of Dr. Halsey, she acknowledged her status as a "copy" of her mind. However, her initial admiration for Dr. Halsey soon turned into hate. Moreover, she considered Dr. Halsey a "monster" post-Rampancy, given her involvement in the SPARTAN-II project. On the other hand, Cortana showed extreme closeness with John-117 to the point that people joke around that they're in a relationship. Cortana believes she is best suited to protect John-117. In fact, some speculate that her "sacrifice" was meant to protect John, not humanity, given her line in Halo 4.
6 Cortana Survived Rampancy
As a Smart AI, Cortana only has around seven years of "functionality" before experiencing Rampancy. In essence, Rampant Smart AIs end up consuming computing power just "thinking" that they forget some of their vital functions. First, Smart AI would demonstrate melancholia — a form of depression when Smart AIs become underutilized or abused. Afterward, they experience anger that will force them to act irrationally. And then, they experience jealousy towards "real" humans, and will try to find "better bodies" for them to develop the same way.
Interestingly, no Smart AI could reach a theoretical fourth stage, Metastability, where AI become "fully human." However, only three AIs fit this category — Cortana, Juliana, and 032 Mendicant Bias.
5 Cortana Had A Unique Take On Metastability
Unlike 032 Mendicant Bias and Juliana, players had a more "concrete" view of how Cortana achieved her Metastability. When Cortana sacrificed her life for John-117, Cortana actually got uploaded into the Forerunner Domain. Forerunners directly "uplink" into the Domain through their armor and access its collective intelligence.
The Domain managed to "cure" Cortana's Rampancy. Some may say the Domain became a "large-enough" space for Cortana to store data she had on the UNSC, the Covenant, and the Flood. In turn, Cortana may have been using the Domain to "awaken" other AI into Created.
4 Cortana Could Have Gone Rampant In The First Game
By the end of the current Halo series, players see Cortana and other AI, now known as the Created, deciding to take on the Forerunner's Mantle of Responsibility and "enforce" their vision of peace throughout the galaxy. In turn, players assume that the next Halo installments would position Cortana as its main antagonist. However, Cortana "going nuts" became an idea that almost came to fruition as early as Combat Evolved.
Apparently, developers reserved an alternate story in Combat Evolved. In it, Master Chief still rediscovers Cortana in the Installation 04 control room. However, this Cortana became mad with power. With the information she's gleaned from the Installation, Cortana would want to take over Installation 04 and even the whole universe.
3 Cortana Can Be Found In Mobile Computers
Interestingly, fans looking for Cortana Easter Eggs may look no further than Halo 3 to find them. In Halo 3, players can search for UNSC mobile computers in order to access this Easter Egg. When looking at the lower-left monitor for a few seconds, Cortana's face appears for just an instant before disappearing.
Players who have a hard time looking for these mobile computers should look for them in the multiplayer map High Ground or at the start of Crow's Nest. This Easter Egg remains a delight for fans, as Halo 3's plot revolves around saving Cortana from the Forerunner Gravemind. In a way, these "Easter Eggs" can serve as Cortana trying to send a call for help.
2 Cortana Could've Had A Different Accent
Fans of Halo would recognize Jen Taylor's voice as the "definitive" voice for Cortana. However, Taylor or another voice actor may have pulled off Cortana with a different accent in the original design document. Apparently, Bungie tasked composer Martin O'Donnell to ensure that the voice actors would've been able to do Cortana's dialogue with an accent similar to that in the British Isles.
Players may notice this desire given some of Cortana's dialogue in Combat Evolved. For instance, Cortana's argument with 343 Guilty Spark featured usage of British idioms such as "Sod off!"
1 Windows Cortana Is Based On Halo's Cortana
People who use Windows PCs nowadays will recognize Microsoft's Cortana smart assistant. Whereas Samsung has Bixby, Amazon as Alexa, and Apple has Siri, Microsoft has Cortana assisting its users. Cortana can recognize natural voices and even answer questions based on information she can gather via Bing. She also has a built-in "Notebook" where she stores contacts, reminders, location data, and interests.
Interestingly, Microsoft took the name "Cortana" from Halo's iconic synthetic intelligence. Microsoft also took Jen Taylor — as in, Cortana's voice actress — to voice Microsoft Cortana's US-version counterpart.